In stringed musical instruments such as guitars and bass guitars, a main component is the neck that provides or supports a fretboard or a fretless fingerboard. The neck is typically made from wood and is ordinarily supplied initially as being nominally straight along its working length, free of neck curvature. The neck is usually attached to an end of the instrument body, however it may extend through the body in special through-neck type instrument construction. The front portion of the neck that is associated with the fretboard/fingerboard may extend part way onto the body.
In conventional wood neck construction, metal frets are inserted individually into transverse slots or channels configured on the front side of the fretboard or neck, where the frets may be held in place by friction-fit alone, depending on close dimensional tolerances in the frets and slots or channels, or further secured by glue.
Typically, in conventional instrument fabrication practice, all frets are initially made to be nominally uniform in height throughout the fretboard region, and in the initial instrument set-up the string-to-fret clearance is first set by the bridge/nut and by neck-truss adjustment (if available) to an overall optimal first approximation.
Due to non-uniformity of conventional wooden materials, even a newly fabricated neck may already have some amount of inherent curvature, concave or convex, and such bowing or arching is not always symmetrical over the neck length, requiring an excessive amount of fret-tip “dressing” by manually filing material from individual fret-tips so as to optimize the string-to-fret clearances individually and collectively.
For stringed instruments in initial setup or refurbishing, a luthier or instrument technician strives to achieve a desired string-to-fret clearance profile throughout the neck-length utilizing all available adjustment capability: e.g. the basic bridge and nut heights supplemented by whatever neck curvature adjustment may be available from a neck truss system to modify the profile of the fret-tips for desired pattern of string-to-fret clearances across and along the length of the neck, with compensation for string thickness.
In instrument set-up by a technician or luthier, even a substantially straight neck with uniform frets and low string clearance throughout the neck length is not considered adequate for optimal performance. The luthier strives to provide “relief”, i.e. a shallow concave curvature in the fret-tip profile over a selected portion of the lower-pitched neck region, typically extending from the second fret to the twelfth fret, and a relatively straight profile throughout the higher-pitched neck region on the same plane as the first fret. After preliminary neck-shaping utilizing truss adjustment to the extent available, “relief” profiling requires special dressing by the luthier judiciously filing material from fret-tips in a lower-pitched region of the fretboard to obtain the optimal overall profile of the collective fret-tips. This is a costly operation, demanding the high skill level and experience of a luthier, that often becomes a tedious trial-and-error process requiring repeated cycles of “dressing” the fret-tips: stringing/unstringing/sanding/filing and crowning, before reaching a satisfactory result.